Birefringence measurements on KTaO₃:Li

Birefringence observations in a single crystal of K1-xLi xTaO3 (x=0.026) indicate a first-order transition to a domain state with sections of large uniform spontaneous polarisation. Measurements under small external electric fields suggest that the main difference with usual ferroelectrics lies in the extremely long relaxation times of the present system. The relation of the author's results with the reported polar glass behaviour of the material is discussed.